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Signs and signals assist with control strategies for intersections and crossings. These intersection control techniques should focus on the goal of safely moving people who are walking, cycling, using transit, and driving, and on reducing overall person delay rather than vehicle delay. Signals directly impact the quality of the transportation system, and the operation of a city’s traffic control system should closely mirror the city’s overall transportation policy goals and objectives.
Amsterdam, The Netherlands
Stop and Yield Control Signs
Stop, all-way stop, and yield signs are applicable to lower-volume urban intersections. They should always be implemented in a way that promotes safe pedestrian crossing. If signs alone are insufficient to create safe crossings, consider geometric measures before signalizing the crossing.
Speed-limit signs are applicable to all urban streets, reiterating overall citywide speed limits as well as specific permissible speeds for shared spaces, laneways, or other slow zones.
Curbside signs communicate rules related to parking, loading zones, restricted access, and other curbside management strategies. In some jurisdictions, signs are legally required for enforceable cycle lanes, transit stops, or transit lanes. Use overhead signs only on multilane streets.
Signals work in tandem with geometric design to create a highly functional multimodal street with safe crossings and intersections. Signal timing influences delay, compliance, speed, and mode choice.
Fixed signal phasing is preferable in urban areas, providing predictability and consistent opportunities to cross streets. Actuated signals and beacons are applicable where pedestrian volume is very low and speed management is not sufficient to create safe crossings.
Signal timing should be managed differently at peak and off-peak times, adjusted to meet different levels of modal activity and different goals throughout the day. See: Design Hour.
Signals should not be considered in isolation, but rather as a system of intersections. Coordinating the timing of crossing corridors is a challenging but high-value traffic management process.
Traffic signal timing with insufficient time for pedestrians to cross a street or long signal cycles that increase waiting times are likely to create an unpleasant or unsafe street, and may discourage walking. Significant delays may cause street users to ignore the traffic signal.
Signal progressions, or green waves, determine the pace of urban streets. Coordinated signal timing synchronizes traffic movements along a corridor and manages the progression speed. A progression speed based on realistic transit and cycle travel speeds, usually in the range of 20-30 km/h, optimizes cycle and transit movements and removes much of the incentive for vehicles to speed. Depending on block length, this progression speed may also synchronize with walking speeds, typically 1 –1.5 m/s.
Long cycle lengths (in seconds) should be used in limited cases as they can divide neighborhoods and make walking or crossing the street frustrating and prohibitive.
Balanced cycle lengths (in seconds) reduce waiting times in all directions and create crossing opportunities at closer intervals.
Multimodal Head Starts, Interval 1. Pedestrians, transit, and cycles are given a head start as they enter the intersection, usually 6 seconds or more.
Multimodal Head Starts, Interval 2. Through and turning traffic are given the green light, as pedestrians, cycles, and transit continues, with turning traffic yielding to pedestrians.
Set signal cycles to accommodate all users. Signal cycles must allow pedestrians moving at different speeds to safely cross the width of the street or get to a refuge space. The graphic shows a 16-m street and the distance people can walk in a 12-s signal cycle.
Signal Cycle Lengths
Though often invisible to the public, traffic signal lengths have a significant impact on the quality of the urban realm and shape how safely pedestrians, cyclists, and transit vehicles interact.
Short Signal Cycle Lengths
For most modes, short signal cycles, usually 60–90 s, minimize delay in a complex network environment. Shorter signal cycles reduce wait times in all directions and create crossing opportunities at closer intervals. Signal phases must account for pedestrian crossing time based on street width and realistic walking speeds.
Long Cycle Lengths
Signal cycles over 90 s can make large avenues into barriers that separate neighborhoods and can make crossing the street or walking short distances frustrating or prohibitive. Long cycles should only be used if necessary to provide pedestrian crossing time on very wide streets.
Two-phase signals are most appropriate at simple, small intersections where geometric design creates low turn speeds. Use pedestrian countdown signals and set clearance intervals for slow pedestrians.
Lagging Left Turn Phases
Turns across traffic present risks to all users on multilane two-way streets. Eliminate left-turn conflicts by providing a dedicated left turn phase after the through vehicle phase.
Leading Pedestrian Intervals (LPIs) and Leading Cyclist Intervals
Provide pedestrians and cyclists a head start before turning vehicles, improving safety and comfort. Time LPIs, at minimum, for a person walking 1.2 m/s to reach the center of the roadway, occupying the crosswalk. Use cyclist signals to provide a leading cyclist interval at the same time.
Multimodal Head Starts
Improve safety and reduce delay for pedestrians and through-moving vehicles, including transit and cyclists in dedicated lanes, by holding turning vehicles at the start of the through phase similar to an LPI. Turning vehicles receive a red arrow, followed by a flashing yellow arrow to indicate the need to yield while turning.
Pedestrian-only/ Cyclist-only Phases
Where pedestrians or cyclists cross diagonally—in complex geometry, high turn volume locations, or on one-way streets with turn lanes—a full-length pedestrian-only phase provides a dedicated pedestrian crossing, but may increase delay or decrease compliance by all users.
Transit Priority Phases
Some active transit signal priority techniques, including transit-only through or turn phases, require dedicated phases.
Adapted by Global Street Design Guide published by Island Press.